Hmmm...just spoke to my dad and he's never heard it before; of course that just means it wasn't in use in Western Colorado in his day. Sorry, T.O.M.

I did find this use of "taw" in Ulysses (my emphasis):

Cyclops

I WAS JUST PASSING THE TIME OF DAY WITH OLD TROY O THE D.M.P. at the corner of Arbour hill there and be damned but a bloody sweep came along and he near drove his gear into my eye. I turned around to let him have the weight of my tongue when who should I see dodging along Stony Batter only Joe Hynes.

-- Lo, Joe, says I. How are you blowing? Did you see that bloody chimneysweep near shove my eye out with his brush?

-- Soot's luck, says Joe. Who's the old ballocks you were talking to?

-- Old Troy, says I, was in the force. I'm on two minds not to give that fellow in charge for obstructing the thoroughfare with his brooms and ladders.

-- What are you doing round those parts? says Joe.

-- Devil a much, says I. There is a bloody big foxy thief beyond by the garrison church at the corner of Chicken Lane - old Troy was just giving me a wrinkle about him - lifted any God's quantity of tea and sugar to pay three bob a week said he had a farm in the county Down off a hop of my thumb by the name of Moses Herzog over there near Heytesbury street.

-- Circumcised! says Joe.

-- Ay, says I. A bit off the top. An old plumber named Geraghty. I'm hanging on to his taw now for the past fortnight and I can't get a penny out of him.

-- That the lay you're on now? says Joe.